PROJECT SUMMARY: This K01 award will provide training and protected time for Dr. Casey P. Johnson, PhD, to develop an independent research program to address a critical need for new imaging solutions to improve the clinical management of developmental hip joint diseases that are precursors to osteoarthritis (OA). As there is no cure for OA and end treatment is total hip replacement, it is imperative to diagnose and treat early hip pathologies before irreversible damage occurs to prevent long-term disability and progression to OA. However, management of these diseases, which include (among others) Legg-Calve-Perthes disease (LCPD) and femoroacetabular impingement (FAI), is hindered by a lack of sensitive and high-spatial-resolution imaging tools to evaluate early, potentially treatable, bone and cartilage damage. To address this challenge, Dr. Johnson will develop and validate techniques to quantitatively assess hip damage using ultrahigh-field (UHF) (?7 Tesla) magnetic resonance imaging (MRI), the technological future for high-spatial-resolution imaging of the musculoskeletal (MSK) system. Dr. Johnson has a strong background in the development of efficient, quantitative, and high-resolution MRI methods and their application to vascular and brain diseases, making him uniquely qualified to advance UHF MRI of multifactorial MSK diseases. During the K01 award?s five-year training period, Dr. Johnson will develop his expertise in MSK imaging research, enhance his professional skills, and establish a network of support within the MSK and MRI research fields. He will be mentored by and collaborate with experts in radiology, orthopaedic surgery, pathology, veterinary medicine, and UHF MRI and receive structured training through coursework, seminars, workshops, scientific conferences, and hands-on experiences. Dr. Johnson?s research will be embedded within the University of Minnesota?s Center for Magnetic Resonance Research, a world-renowned research environment for the development and application of UHF MRI technology. Two specific aims will provide training in: (i) preclinical imaging of specimens using a small-bore 9.4T MRI system with histological validation; and (ii) clinical imaging of patients using a whole-body 7T MRI system with surgical validation. Aim 1 will develop and histologically validate, in a piglet model of LCPD, techniques to quantitatively assess early ischemia-induced changes to femoral head marrow, cartilage, and bone. This will address a need to stage LCPD in children prior to femoral head fragmentation. Aim 2 will develop and arthroscopically validate, in patients with FAI, techniques to quantitatively assess cartilage and labral damage. This will address a need to determine the extent of damage to identify candidates for reparative arthroscopic surgery. UHF MRI development will focus on T2, T2*, and T1? mapping using both short and ultrashort echo-time sequences to quantify tissues with both slowly- (cartilage and marrow) and rapidly- (bone and labrum) decaying MRI signals. This research will provide Dr. Johnson with a strong foundation to advance imaging to improve long-term clinical outcomes for young patients with hip and other joint diseases.